Rooftop Exhaust System for Exhausting Air from a Building

ABSTRACT

The present invention entails a rooftop exhaust system for a building. The exhaust system includes a motor that is configured to directly drive a fan. The fan during the course of operation generates a negative pressure on the upstream side of the fan. This negative pressure is utilized to induce outside cooling air into a shroud that partially encloses the motor. Cooling air passing through the shroud contacts the motor and heat associated with the motor is transferred to the cooling air after which the cooling air exits the shroud.

FIELD OF THE INVENTION

The present invention relates to rooftop exhaust systems that exhaust air from buildings.

BACKGROUND OF THE INVENTION

Many buildings employ rooftop exhaust systems for exhausting air from the building. Typically, rooftop exhaust systems include a motor that drives a fan. In some applications, the air being exhausted by the exhaust fan can be relatively hot and this can have adverse effects on the motor. In these cases, the motor is asked to perform in a hot environment. This hot environment impacts the performance and life of the motor which in turn results in the motor requiring replacement too often and also contributes to increased maintenance cost.

Hence, there is a need for a rooftop exhaust system designed to minimize heat buildup in and around the motor. Further, there is a need to incorporate into the exhaust system features that positively cool the motor when the exhaust fan is operating.

SUMMARY OF THE INVENTION

The present invention relates to a rooftop exhaust system for exhausting hot or warm air from a building. The exhaust system includes a motor which drives a fan. To protect the motor from hot or warm air passing through the exhaust system, a partially open shroud extends around the motor. As the fan is driven, a region of negative pressure forms between the fan and the motor. The shroud is open to this negative pressure. Due to the negative pressure, ambient cooling air from outside of the building is directed into and through the shroud. As the cooling air moves through the shroud, it contacts the motor and in the process cools the motor.

In one particular embodiment, the motor and fan are supported inside a housing having a wall. The shroud is also mounted in the housing and extends around the sides and bottom of the motor but is open at the top. The shroud generally isolates and protects the motor from hot air that is being exhausted from the building. However, the shroud is open at the top. Hence, the opening in the top of the shroud lies below the fan. The wall of the housing is provided with one or more cooling air inlets. The cooling air inlets formed in the housing are connected to one or more air cooling conduits. The air cooling conduits are in turn connected to cooling air inlets formed in the shroud. As noted above, when the fan is operating, a region of negative pressure lies between the fan and the motor. Since the shroud is open at the top, it is open and exposed to this negative pressure. This negative pressure that lies about the top opening in the shroud causes ambient cooling air to be induced into the cooling air inlets in the housing. From there, the cooling air enters the cooling air conduits that directs the cooling air into and through the shroud and out the open top thereof where the cooling air joins with the exhaust air from the building. The continuous flow of cooling air through the shroud results in the cooling air continuously contacting the motor and in the process cooling the motor.

Other objects and advantages of the present invention will become apparent and obvious from a study of the following description and the accompanying drawings which are merely illustrative of such invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevational view showing the rooftop exhaust system incorporated into the roof of a building.

FIG. 2 is a perspective view of the rooftop exhaust system.

FIG. 3 is another perspective view of the rooftop exhaust system showing it from the bottom.

FIG. 4 is a schematic sectional view showing the exhaust system, as well as the flow of the exhaust air and cooling air.

DESCRIPTION OF PREFERRED EMBODIMENT

With further reference to the drawings, an exhaust system is shown therein and indicated generally by the numeral 10. See FIG. 1. In the embodiment illustrated, the exhaust system is what is generally referred to as an upblast-type. Conceptionally, the present invention can be employed with other types of exhaust systems. Exhaust system 10 is used for general ventilation. As shown in FIG. 1, the exhaust system 10 is installed on the roof of a building. Exhaust system 10 is mounted on a curb 13 which in turn is supported on the roof of the building. In operation, the exhaust system 10 exhausts air from the building, resulting in exhaust air being drawn towards the roof of the building and into and through the curb and out the exhaust system.

Exhaust system 10 includes a housing indicated generally by the numeral 12. It is appreciated that the specific design and construction of the housing can vary from one application to another. In any event, in the embodiment illustrated herein, housing 12 includes a lower housing 12A that can assume a generally rectangular, square, or round configuration. In the particular embodiment illustrated, the lower housing 12A includes a plurality of side walls 12C. Housing 12 further includes an upper housing 12B that extends upwardly from the lower housing 12A and functions as an air duct for directing exhaust air upwardly through a portion of the exhaust system. Upper housing 12B is sometimes referred to as an air shaft. In the embodiment illustrated, the upper housing 12B assumes a generally circular form.

Exhaust system 10 is provided with means for inducing exhaust air to move upwardly through the exhaust system where the air is exhausted to the atmosphere. In the application illustrated, the housing 12A is mounted on a curb 13. See FIG. 1. Hence, when the curb 13 is used, exhaust air from the building moves from the building through the curb 13 and then through the exhaust system 10. Various fan and motor arrangements can be incorporated into the exhaust system. In an exemplary embodiment, the exhaust system includes a propeller 16 which is directly driven by an axially aligned motor 18. Motor 18 is supported by a frame structure in the housing 12. Note that the propeller 16 and motor 18 are axially aligned with the upper circular housing or air shaft 12B. It is appreciated by those skilled in the art that a fan wheel may be used in lieu of the propeller 16. It is understood and appreciated by those skilled in the art that other types of fans can be incorporated into the exhaust system 10. As used herein, the term “fan” includes propeller-type fans and wheel-type fans. As noted above, in the arrangement shown in the drawings, propeller 16 is directly driven by the motor 18. Generally when a direct drive is employed, the propeller is mounted to the drive shaft of the motor 18 or to an extension therefrom. In other cases, the propeller or fan wheel can be driven from a side mounted motor through a belt drive.

Supported at the outlet end of the upper housing 12B are one or more dampers 30. In the embodiment illustrated, there is provided two dampers 30 with the dampers being pivotally mounted about a transverse axis about the top of the upper housing 12B. Thus, the dampers 30 are supported, at least indirectly, by the upper housing or air shaft 12B. As seen the drawings, the dampers 30 are disposed over the propeller 16 and motor 18. Since the dampers 30 are pivotally mounted, they are moveable from a generally horizontally closed position to a raised or inclined open position. See FIG. 2. In a normal operation, the force of the air being exhausted upwardly through the exhaust system is sufficient to open the dampers 30 so as to permit the exhaust air to escape.

A shroud 32 is mounted in the housing 12. Shroud 32 can assume various shapes and configurations. In the embodiment illustrated in the drawings, the shroud 32 includes multiple sides, a bottom and an open top. Note that the shroud 32 is disposed around the motor 18. See FIGS. 3 and 4. Shroud 32 generally isolates the motor 18 from the grease laden exhaust air passing through the housing 12. As seen in the drawings, shroud 32 extends approximately the full length of the motor 18. That is, the walls of the shroud 32 can terminate below the top of the motor, even with the top of the motor or above the top of the motor. As noted above, the specific design of the shroud 32 and its orientation in and around the motor 18 can vary. Also, as people of ordinary skill in the art appreciate, the material used to construct the shroud 32 can vary but it is preferable to use a material that provides a good thermal insulation.

The exhaust system 10 of the present invention is designed to induce ambient cooling air from outside of the building into the shroud for the purpose of cooling the motor 18. This is achieved by the provision of one or more air cooling inlets 34 formed in the side walls of the housing 12A. In the case of the embodiment illustrated, there are two air cooling inlets 34 but it is understood that there could be one or a multiplicity of air cooling inlets. There is also provided air cooling inlets 36 formed in the shroud 32. Here again in this particular embodiment, there are two air cooling inlets 36 formed in the walls of the shroud 32. Air cooling inlets 34 and 36 are connected by air cooling conduits 38. As will be appreciated from the discussion below, the function of the air cooling conduits is to channel cooling air from the air cooling inlets 34 and the housing 12A to the shroud 32.

During the operation of the exhaust system 10, the propeller 16 will generate a negative pressure zone 40 on the upstream side of the fan 16. This negative pressure zone 40 is illustrated particularly in FIG. 4. Note that the propeller 16 is fixed to the output shaft of the motor 18 and that the top of the motor is spaced relatively close to the propeller 16 and the open top of the shroud 32. The negative pressure zone 40 stretches across the open top of the shroud 32. Because the top of the shroud is open, the shroud and the interior thereof includes the negative pressure generated by the propeller 16 during the operation of the exhaust system. More particularly, the negative pressure in and about the shroud causes outside or ambient cooling air to be induced into the air cooling conduits 34 formed in the side wall 12C of the housing 12A. From the air cooling conduits 34, the cooling air is induced to enter the air cooling conduits 38 after which the cooling air flows into and through the internal areas of the shroud 32. This cooling air contacts the motor 18 and heat is transferred from the motor to the cooling air as it flows through the shroud 32. Because the top of the shroud 32 is open, the cooling air that exits the shroud 32 is mixed with the exhaust air and together they are exhausted from the exhaust system via the upper housing 12B. In FIG. 4, the cooling air and the exhaust air are referred to by arrows. Arrows with dotted line tails represent the exhaust air and arrows with full line tails represent the cooling air.

The exhaust system of the present invention is useful for more than cooling the motor 18 during normal operations. In addition, the exhaust system is designed to keep the motor 18 running in case of a building fire. With the addition of the cooling conduits and the shroud, the motor 18 can run continuously when exposed to a temperature of up to 572° F. and can run up to four hours when exposed to a temperature of 1000° F. In the case of a building fire, the exhaust system pulls smoke out of the building and this improves visibility inside of the building for occupants and firefighters.

In the specification and claims, the term “configured to” is used. The term “configured to” is defined to mean “designed to”. The term “configured to” is more narrow than terms such as “for” and “capable of”.

From the foregoing specification and discussion, it is appreciated that the present invention is a relatively simple, efficient and cost effective way of cooling the motor 18 that forms a part of a rooftop exhaust system. It is particularly efficient and cost effective since the negative pressure generated by the propeller in the course of exhausting air is employed to induce the cooling air into and through the shroud 32.

The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the scope and the essential characteristics of the invention. The present embodiments are therefore to be construed in all aspects as illustrative and not restrictive and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. 

What is claimed is:
 1. A method of exhausting air from a building with a rooftop exhaust system comprising a housing, a motor, a shroud at least partially encompassing the motor, and a fan directly driven by the motor and wherein the motor, shroud and fan are generally disposed in the housing, the method comprising: driving the fan and inducing exhaust air to move from the building through the housing and out an outlet of the rooftop exhaust system; generating a negative pressure in a zone that lies on an upstream side of the fan and adjacent an opening provided in the shroud; wherein the negative pressure induces outside cooling air to enter one or more air cooling inlets formed in the housing; directing the cooling air from the air cooling inlet in the housing to one or more conduits extending through the housing and between the air cooling inlet in the housing and one or more air cooling inlets formed in the shroud; directing the cooling air from the air cooling conduit through the air cooling inlet of the shroud and into and through the shroud; cooling the motor within the shroud by contacting the motor with the cooling air passing through the shroud; discharging the cooling air from the shroud through the opening; and after discharging the cooling air from the shroud, mixing the cooling air with the exhaust air.
 2. The method of claim 1 wherein the shroud includes a side wall structure that extends around the motor and a bottom that lies underneath the motor; and wherein the opening is formed in the top of the shroud and faces the fan.
 3. The method of claim 1 wherein the exhaust air passes around and outside of the shroud and wherein substantially no exhaust air directly contacts the motor.
 4. A rooftop exhaust system for exhausting exhaust air from a building comprising: a housing having one or more side walls and configured to be mounted on the roof of the building; a motor mounted in the housing; a direct drive fan operatively connected to the motor for inducing the exhaust air to flow into an inlet end of the housing and through the housing; a shroud disposed in the housing and extending at least partially around the motor and configured to generally isolate the motor from exhaust air passing from the building through the housing; the shroud is generally enclosed except for an open top that faces the fan; one or more air cooling inlets formed in the shroud; one or more air cooling inlets formed in the side wall of the housing; one or more air cooling conduits connected between the air cooling inlet formed in the shroud and the air cooling inlet formed in the housing; wherein the fan is configured to generate a negative pressure zone on an upstream side of the fan and by virtue of the negative pressure zone, the fan is configured to induce cooling air to flow from outside of the building into the air cooling inlet in the housing, through the air cooling conduit and into and through the shroud where the cooling air cools the motor; and wherein the rooftop exhaust system is configured to discharge the cooling air from the open top of the shroud where the cooling air mixes with the exhaust air.
 5. A method of exhausting smoke from a building fire with a rooftop exhaust system comprising a housing, a motor, a shroud at least partially encompassing the motor, and a fan directly driven by the motor and wherein the motor, shroud and fan are generally disposed in the housing, the method comprising: driving the fan and inducing smoke to move from the burning building through the housing and out an outlet in the rooftop exhaust system; as the building burns, running the motor continuously when the motor is exposed to a temperature of up to 572° F. and running the motor for a period of four hours or less when the motor is exposed to a temperature of 573° F. to 1000° F., wherein running the motor under said temperature conditions and during a building fire include: generating a negative pressure in a zone that lies on an upstream side of the fan and adjacent an opening provided in the shroud; wherein the negative pressure induces outside cooling air to enter one or more air cooling inlets formed in the housing; directing the cooling air from the cooling air inlet in the housing to one or more cooling conduits extending through the housing and between the air cooling inlet in the housing and one or more air cooling inlets formed in the shroud; directing the cooling air from the air cooling conduit through the air cooling inlet of the shroud and into and through the shroud; cooling the motor within the shroud by contacting the motor with the cooling air passing through the shroud; discharging the cooling air from the shroud through the opening in the shroud; and wherein the discharged cooling air from the shroud mixes with the smoke being exhausted by the exhaust system. 